January 12 in Eastern Orthodox liturgical calendars is a feast day and a day of commemoration of saints and martyrs. Although some Orthodox churches use the Revised Julian Calendar and others use the traditional Julian calendar, the fixed commemorations for their respective January 12 are broadly the same, no matter which calendar is used.
Afterfeast of the Theophany of Our Lord and Savior Jesus Christ
Virgin Martyr Tatiana of Rome, and those who suffered with her (226-235)
Martyr Mertius of Mauretania (284–305)
Martyr Philotheus of Antioch (c. 305)
Martyr Peter Apselamus of Eleutheropolis, Palestine (309-310) (see also January 13, and October 14)
Venerable Eupraxia of Tabenna, Egypt (393)
Saints Tygrius the Presbyter, and Eutropius the Lector, at Constantinople (c. 395 - 408) (see also: June 16)
Holy Eight Martyrs of Nicaea, by the sword.
Virgin Martyr Euthasia, by the sword.
Venerable Elias the Hermit, Wonderworker of Egypt, Desert Father, of The Paradise (4th century) (see also January 8)
Saint Eulogia, mother of Saint Theodosius the Cenobiarch (4th century)
Venerable Theodora of Alexandria, instructress of nuns (5th century)
Saint Arcadius of Mauretania, a prominent citizen of Caesarea in Mauretania Caesariensis, barbarously martyred under Maximianus Herculeus (c. 302)
Martyrs Zoticus, Rogatus, Modestus, Casutlus, between forty and fifty soldiers, in Africa.
Saint John of Ravenna (Giovanni I Angelopte), Bishop of Ravenna and Confessor (494)
Saint Caesaria, the gifted sister of Saint Caesarius of Arles and Abbess of the convent founded there by her brother (c. 530)
Saint Victorian of Asan, founder and abbot of the monastery of Asan (now called San Vitorián) (c. 560)